This invention relates to a method of controlling automatic stop and restart of an engine for automatically stopping an engine under some predetermined conditions, and thereafter, automatically restarting the engine under other predetermined conditions.
In general, during running on a road, when a vehicle has to be stopped for a long period of time because of a traffic jam due to a signal waiting, an accident caused by another vehicle or the like, an engine may be temporarily stopped, and thereafter, restarted after the traffic jam has gone. This is done so as to avoid useless fuel consumption due to an idle operation for a long period of time.
Referring to the running through an urban district, the periods of time for vehicle stopping in the urban district comprises a fairly large percentage of the whole operating time of the vehicle, and the amount of exhaust gases and the quantity of fuel consumed therefor are not neglectable. Therefore, it is conceivable that, upon stopping of the vehicle for the signal waiting and the like during running in the urban district, the engine of the vehicle is stopped by manual operation. However, the stopping of the engine by manual operation each time of the signal waitings leads to the manually engine restarting operation, thereby resulting in a troublesome operation and a delayed starting operation of the vehicle.
There has heretofore been developed an automatic engine stop-restart system wherein, when a motor vehicle is stopped at an intersection or the like during running through an urban district, if it is desirable to temporarily stop the engine for the purpose of improving the fuel consumption rate, the engine is automatically stopped, and thereafter, automatically restarted by a normal starting operation, which is effected at the time of starting the vehicle, such as a depression of a clutch pedal.
In the conventional system of the type described, when a starting signal is fed to a starter in operational association with a clutch operation to restart the engine, judgement of necessity for cutting off this starting signal has been obtained when either one condition (1) "the engine rotational speed exceeds a predetermined value (550 rpm for example)" or the other condition (2) "the alternator is in the generating condition" is fulfilled.
However, if judgement is obtained based on either one of the above-described conditions, then there has been presented such a disadvantage that, when information of the engine rotational speed cannot be obtained due to a trouble caused to the sensor for example, regardless of rotation of the engine, the starter is driven, thus resulting in a damaged starter.